This invention relates to electromechanical memory assemblies for data processing systems; and in particular, it relates to the packaging of such assemblies.
By an electromechanical memory assembly is herein meant an assembly of multiple data storage units each of which reads and writes data by physically moving a data storage medium past a data sensor. Two common examples of such data storage units are disk drives and tape drives.
In the prior art, various standard interfaces have been defined for disk drives and tape drives which specify how they are to be intercoupled in an assembly. One such standard called ESDI specifies the interface coupling for disk drives; whereas another standard called QIC-02 specifies the interface coupling for tape drives.
Basically, with the ESDI disk interface, control signals are daisy-chained from a disk controller to all the drives, and data signals are sent radially between the controller and each drive. With the QIC-02 tape interface, both control and data signals are daisy-chained between a tape controller and all of the tape drives.
Also, with both of the ESDI and QIC-02 interfaces, switches or jumpers are provided on each drive which must be set to assign that drive a unique address. This unique address enables the drives to be individually selected and operated one at a time via the interface signals. Further, with both interfaces, sockets for receiving resistors which terminate the daisy-chained signals from the controller are provided in each drive, and the terminating resistors must be inserted in the socket of only the last drive of the daisy chain.
Accordingly, to initially install the drives of a multidrive memory assembly, all the daisy-chained cables must be correctly connected; all the radial cables must be correctly connected; all the address switches in the drives must be differently set; and the terminating resistors must be inserted in the last drive only. These steps, however, are time-consuming and are susceptible to human error. Further, in many electromechanical memory assemblies where a premium is placed on space, the cables and drives are squeezed into a small frame and are difficult to even reach.
Similar problems are also encountered when a new drive is added to an existing memory assembly. To add the new drive, another daisy-chain cable has to be connected between the existing last drive and the new drive; the terminating resistors have to be moved from the existing last drive to the new drive; a radial cable (in the case of a disk) has to be connected between the controller and the new last drive; and the address switches have to be set to a unique address in the new drive.
Recently, memory "filecards" have been introduced into the market which do simplify the installation procedure for a single drive. A filecard is a printed circuit board which contains a controller and to which a drive mechanism is attached in a piggyback fashion to the back of the board. See, for example, Mini-Micro Systems, April 1968, pages 28 and 32. To install such a filecard, the card is simply plugged into a connector in a backplane. Cabling between the controller and the drive runs off the back of the board to the piggybacked drive and is installed at the factory.
However, these filecards are not suitable for multidrive memory assemblies. To add another drive, another new filecard which includes both the drive mechanism and the controller must be added. This is not economical since the controller portion of the card costs about the same as the drive portion of the card. If one were to somehow mount just a bare drive in the assembly, cabling would still have to be installed between the piggybacked drive on the drivecard and the new drive which complies with ESDI, QIC-02, or a similar standard. Terminating resistors would also have to be moved to the new drive; and a unique address would have to be set. But such installation steps would again be time-consuming and accompanied by human error.
Accordingly, a primary object of the invention is to provide an electromechanical memory assembly which overcomes the above described deficiencies.